There is known a slotless type optical cable in which a plurality of optical fibers is disposed within a sheath. Patent literature 1 and Patent literature 2 disclose an optical cable in which the cross-sectional surface of a housing portion for housing optical fibers is non-circular.
Strength members (tension members) are embedded in the sheath of the optical cable (see Patent Literature 1 and Patent Literature 2). Metallic wires such as steel wires are generally used for the strength members. Whereas, in the case where metallic wires are used for the strength members, a lightning surge may travel along the strength members, and thus a nonmetallic material such as glass FRP (GFRP) may be used for the strength members.